Scanning system



XR 29010976Q Aug. 6, 1935.

J. v. L. HOGAN SCANNING SYSTEM Filed Feb. 10, 1951 Jm Vliibywm IN VENTOR.

2010? 43m- QB? cmssz Patented Aug. 6, 1%35 j 2,010,764 SCANNING SYSTEM.llohn V. LLHogan, Forest Hills, N. Y., assignor to Radio Inventions,Inc,

4 poration of NewYork New York, N. Y., a cor- ApplicationFebruary 10,1931, Serial No. 514.717

' iClaims. (o1. 1786) Myinvention relates to-a method and apparatus forthe optical scanning of an image', f r television or other purposes. The-fundamental principle of scanning by optically dividing a field of viewinto a number of elementary areas and exposing alight sensitive devicesequential- 1y. to the light proceeding from each of theseelementaryareas is well known in the art. --This invention relates moreparticularly to the apparatus employed for securing this sequential exposure, and itslanalog at the receiver for sequentially exposing theelements of the-field of view to light from a source modulated by thesignals from the transmitter. r

. Devices of this character usually scan bysome form of mechanicalmotion, vibratory or rotary. One common form of scanner moves a-seriesof apertures before the field, which apertures may be physicallyexistent upon a single moving member. oronly virtually formed by thecoaction of two or more series of apertures in separate members, whosepositions .and movementsare so coordinated that theshifting intersectionof the separate seriesof apertures scansthe field.

, One-widely employed scanner has a series of aperturesspirally disposedupon a rotating disc, and will be hereinafterreferred to as'a Nipkowdisc. As one representative of another class where a plurality of moving,members. are employed, the scanner disclosed in the'co-pen'dingapplication of Harold P. Donle, Serial No. 425,785,

* will be hereinafter referred to as a drum and disc scanner; c r Inconnection with the scanning. process it has been found that for.various reasons it is possible to secure an apparently better reproducetion of theordinary fieldof view when the num'- ber of elements, intowhich the field is divided are not distributed evenly between the twodi-' mensions, but are made greater in one dimension, usually thehorizontal one.- Thismethod ofscanning isset forth in detail in'the'co-pending application of Harold P. Donle, Serial No. 433,670, and willbe hereinafter referred to as high'detail scanning: 1 y One object of myinvention is to, provide greater illumination byadmitting the passage ofmore light in at least one direction of the elementary area thanwouldpass through a similarly employed slit. I J Another :object of thisinvention is to allow high detail scanning. to. be practiced in eitherdirection without decreasing the illumination'in that direction. Anotherpurposeis to allow high detail scan-,

ning in one direction to be combined with greaterbrilliancy inthe samedirection.

' Astill further object is to allow more light to pass inbothdimensions, by the use of my invention with a 'pluralityof scanningmembers.

In transmitting scanners of the moving spot of light type, anotherobject'is to allow great er illumination from a given source of light,than could otherwise be obtained.

-In transmitters of'the total subject illumina tion type, an object ofmy invention is to allow a greater area of the light-sensitive celltoreceive the light from a single elementaryscanning area, than wouldotherwise be possible.

' Other objectsof my invention will be evident from the followingspecifications and drawing,

Fig. 1 represents a front elevation of one form of scanner utilizing myinvention suited for scanning in one dimension only.

Fig. 1a shows a perspective sectional view of the, edge of the disc ofFig. 1; illustrating one method of arranging the lenses relative tothesurface of thedisc. I L v Fig. 2 isa sectional view of apparatusembodying my invention and suited for scanning-tmotion-picture film.Fig. 3 is a View of a 'device for scanning-in both dimensionssimultaneously.

Fig. 4 is an enlarged detail view showing one form oflimiting-diaphragm. f v Fig. 5 illustrates another form of lens,whiclimay be used according to my invention and is of especial value whenthelenses are radially placed. Fig. 6 shows another form oflens suitedfor exerting unequal magnification in two dimensions, andyet giving asubstantially rectangular field of" magnification, when radiallydisposed upon'adisc'or the like.

The broad idea of my invention is the replace ment of slits orperforations in scanning devices by cylindrical lenses, which will actto concentrate the 1 light in at least one dimension. In this fashion ascanning element can be of a given idth and yet pass as much light asthough it were much wider. Thus the detail of scanning can be preserved,and ahigherproduct'ofillumination times area be secured. This means agreater brilliancy of the image at the receiver or a greater response ofan appropriate'light-sensitive cell at the transmitter."

It is also possible with the use of my" inven'-' tion so to choosethe'cylindrical lenses that the light passing. therethrough will benarrowed still and brilliancy.

dimensions within the frequency limits of trans.-

mission. It may be used in one dimension so as to increase thebrilliancy, and in the other dimension so as to increase the detail, ordetail In Fig. 1 the scanning'disc 1, rotating as indicated by the arrow8, is provided with cylindrical lenses 9, arranged about itsouter edge,with, their axes lying substantially along radii of the disc. A disc ofthis type operates to scan a scene inone dimension only. Scanning inthe. other direction may be accomplished by another scanning member,(not shown) such as a slow-moving slitted disc, a mirror drum or thedrum of the drum disc type scanner. If motion picture film is beingscanned, the film itself may conveniently be continuously in motionalong its length past a slit which delimits the scanning area in thisone dimension. This method of operation is in accordance with thescanning method disclosed in the co-pending Patent application SerialNo. 433,670 of Harold P. Donle.

If the other scanning element is in motion relative to disc I, thelenses9 must be of sufiicient length so that some portion of the lensshall atall times be in a position to co-operate with the other scanningelement. ment bestationary relative to disc I, only a portion of thelens, optically equivalent in length to the width of the other scanningdimensions, needs-be used. Therefore the cylindrical lenses can be madevery short in this latter case. t Fig; 2 shows a lens 9 passing by afixed aperture l 0, before which moves continuously motion picture filml l. Light from source I2 fed with energy through terminals I6 andconductors ll passes through the film H, the slit in, the lens 9 and:finally impinges on the photo electric cell [3, having terminals I 4 andoutput conductors l5. While only a lamp is shown herein, it is to beunderstood that inpractice suitable optical means,'such as lenses and/orreflectors and/or the. like may be employed in conjunction therewith tosecure greater efliciency and/or other well known advantages.

In Fig. 3 the scanning disc I, rotating as indi- .cated by the arrow 8'has the cylindrical lenses 9" disposed in spiral contour thereon, butwith their axes radially placed. In this form scanning in bothdirections simultaneously takes place by the movement of the singledisc. It is necessary, however, with this. form to provide synchronousmeans preferably rotating withthe disc, which shall act to limit theheight of an elementary area, in the radial direction. One convenientmeans for accomplishing this purpose is to have the openings in the discbefore each lens take the form of narrow slits, of width correspondingto the height of the elementary area. In this form of my invention thelength of the lenses need only be suflicient to cover such limitingslits as have just been described.

portion of the. form of Fig. 3, enlarged and show However if this ele--ing the use of a limiting diaphragm 2| with an aperture 22 extendingacross lens 9'. This diaphragm may be fastened to the disc by clampingmeans as indicated at 23, and may be fiat as indicated or may lie closeto one surface of the lensyor can be a slit in an opaque painting on oneor both surfaces thereof.

The mode of operation of my invention is according to procedures wellknown in the art and will be readily apparent to one skilled therein. Itcan be employed in connection with various other devices to constitute acomplete television system. While my invention can be used with lightsensitive cells and light producing means of existing types, its optimumaction is to be secured when the photo-electric cell has its sensitivesurface or the reproducing device its light reproducingsurface,,respectively, so dimensioned and arranged that the'lightproceeding thereunto from the cylindrical lenses, or collected therefromby thelenses, shall cover or proceed from such surface in its entirety.l I In the case of the form of my invention shown in Fig. 1, used with amoving member for scanning in the other dimension, or in the case ofFig. 2, the surfaces which would be sufiicient for use with an ordinaryapertured disc may well be enlarged in order that the area correspondentto the light gathering or displaying powers of the lenses shall beuniform throughout the area scanned. This means an enlargement in adirection at right angles to the axis of the lenses. In the case. of afilm moved past a stationary slit as with the scanner of Fig. 1, thephoto-electric cell or reproducing lamp. can have one dimensionreducedto a value correspondent to the width of the fixed slit, while the otherdimension is increased to accord with the lens coverage, as in the caseof the preceding forms.

This smaller total area may allow greater use of such area, since theportion of the total area in use at. any one instant can then berepresented by a fraction whose denominator is the ratio of the totallength covered by the lens in a direction at right angles to its axis tothe length covered at any single instant. In the case of the scannerwith elements moving in both dimensions the denominator of this fractionwill be the total number of elements into which the areais to be dividedby the combined action of the scanning in both directions. While anysuitable number of lenses may be employed according to my invention, Ihave shown 12 in Fig. 1, which would give 24 line scanning at 15pictures per second, if the discrevolves 1800 f I do not confine myinvention to the illustra-,

tive values just given, however.

When my invention is employed'with a single disc such as that of Fig. 1,it is possible to move the light source itself in order to securescanning in the other dimension. Inthis'case the light source can benarrowed in one dimension, with consequent economy of energy andincreased efficiency. This method of scanning in one dimension by theuse of a moving source of light forms the subject of my co-pendingapplication Serial No. 495,601. In this latter case it may also beadvantageouslto employ a cylindrical lens in conjunctionwith each ofthemoving sources of. light, in case that these sources are wider thannecessary to cover a single elementary area.

It is likewise possible to use two'moving members, each bearingcylindrical lenses in accordancewith this invention, and co-operatingwith a fixed source of light, in the case of a receiver or with theilluminated image and the photoelectric cell in the case, of atransmitter. Thus greater concentration of light will be secured in bothdimensions.

In all cases of the use of cylindrical lenses according to my invention,it may be found to be advisable or necessary to use in conjunctiontherewith, aperture slits, which shall cut the fringes of the light rayspassed by the lenses, in order to secure more perfect definition of theedges or the focus thereof, after the manner well known in the opticalart. Even if the employment of such aperture slits be needed, yet therewill still remain a. greater passage of light by the use of my inventionthan would be possible by the use of slits or holes alone, as has beencustomary hitherto in the art.

Due to the radial placement of the lenses of my invention, when they areemployed upon a disc as in the case of Fig. 1, the portion of the lensnearer to the centre of revolution will not traverse a space as great asthe portion which is nearer the periphery of the, disc. As a consequenceof this action, the image produced by such a disc 1 having slits thereonwhen used with a co-operating member with apertures moving radially inref erence to the'disc would not be strictly rectangular, but wouldrather be the outer section of a sector of a circle, its sides beingbounded by radii of the same. The same effect arises from the individuallenses of Fig. 3 being radially displaced relative to one another. Inthe case of a disc provided with the cylindrical lenses of my invention,it is possible to compensate for this error, by fitting the lenses sothat their axes are not in, or parallel to the plane of the disc itself,but are inclined thereunto. Due to the divergent character of the lightrays passing through such lenses this angular placement can be adjustedso that the light passing through the portion of the lens nearer to thecentre will actually traverse a space as great as that passing throughthe portion of be that correspondent to the peripheral separation of theradial lenses rather than that correspondent to the shorter distance bywhich they are separated near to the centre. Therefore the effectivewidth of the image may be made greater and more nearly or exactlyuniform by this mode of construction.

While I have shown the cylindrical lenses in the illustrative figures asbeing of the double cylindrical type of lenses, it is to be understoodthat I do not confine myself to this particular type of cylindricallens, but plano-convex or other types may be employed. The use of theterm cylindrical lens is designed to cover broadly lenses which refractlight to much greater degree along one axis than along an axis at rightangles thereto.

In employing my invention with disc like structure, it is also possibleto correct for the radial error due to the placement of the lenses bythe employment of lenses not mathematically cylindrical but, with one ormore faces tapered'or of varying degrees of curvature so as tomodiiy'their refractive powers according to the distance of a given spotfrom thecentre of. the'disc. These lenses mightbe said to'be conical incharacter.

While theinvention has been described largely in terms of the actionoflenses whichrare'plane in one dimension and-curved in the other, i. e.,the conventional type of cylindrical lens, I contemplate the use of'lenses having curvature in both dimensions. By using a slight curvaturein the radial dimension of Fig. 1, together with a greater curvature inthe circumferential dimension as in Fig. 6, I may control separately twoimportant functions of lenses in scanning systems by varying (indesigning the lenses) the degree of light concentration produced in thedirection of scanning motion and at right angles thereto. Such lensesare sometimes called ellipsoidal,

though I prefer the term substantially cylindrical.

My invention of the use of cylindrical lenses may also be combined withthe use of a disc bearing a small number of lenses rotated at a highrate of speed, co-acting with a shutter member to give the equivalenteffect or" a larger number of lenses I operated at a lower speed. As anexample of such an arrangement, reference may be made to the co-pendingapplication of Harold P. Donle, Serial No. 328,337, wherein a discbearing a plurality of.

convolutions is shown. A single cylindrical lens may be substituted foreach radially disposed series of apertures of that'disclosure, andappropriately arranged shutters coact therewith to give the effect of aplurality of cylindrical lenses. This 1. In television scanningapparatus using radially disposed scanning apertures, means forproducing a substantially rectangular picture in-- cluding lensesatleast partially of a conical character and tapering substantially inproportion to the radial angle at which said lenses are placed.

2. In television scanning discs, means for reducing the distortion dueto radially placed optical apertures, including tapered cylindricallenses whose curvature varies substantially in accordance with theradial. distance of the different portions of said lenses.

3. A television scanner including means for moving motion picture filmso as to scan in one direction, a stationary screen having an aperturelimiting the optically active portion of said film in the dimensioncorresponding to the direction of motion of said film to a fractionalpart'of a complete image, a stationary light source illuminating saidactive portion of said film, a series of lenses having differingrefractive powers in two dimensions moving substantially at right anglesto said motion picture film and coacting therewith and with saidstationary screen so as to scan in the other direction and defining anelemental scanning area in said other direction.

4. A television scanner including means for moving motion picture filmso as to scan in one direction, a stationary screen having an aperturelimiting the optically active portion of said film inthe dimensioncorresponding to the direction of motion of said film to a fractionalpart of a complete image, a stationary light source illuminatin havingdiffering refractive powers in two dimensions moving substantially atright angles to said inotionfpic'turefilm and coacting therewith andwith" said stationary screen so as to scan inthe other direction, and aplurality of shutters one over each of said lenses, said lenses and saidshutters defining an elemental scanning area in said said active portionof said film, a series of lenses other direction. v

I a JQHN V. L. HOGAN.

